1. Field of the Invention
The present invention relates to serial data transmitter/receiver systems, and more particularly to a last word monitor system which cooperates with an ARINC 629 terminal controller.
2. Description of the Related Art
The operation of aircraft relies heavily on many electrical avionic subsystems for successful flight missions. These electrical subsystems include, among others, flight management, navigation, auto-pilot, global positioning systems, landing systems, fuel quantity systems, and the like. Many of these electrical subsystems require communications therebetween, and some sensing subsystems may be located remote from the processing subsystems. Since many of these subsystems may be provided by different manufacturers, standards have been defined for the transfer of data messages on data buses that are wired throughout the aircraft. One such standard is the ARINC (Aeronautical Radio Incorporated) 629 Standard.
The ARINC 629 Standard is such that each data message consists of a plurality of data words of fixed length, i.e., a fixed number of bits. Further, the data message format always consists of a label word, which indicates which subsystem transmitted the data message, followed by one or more data words. The ARINC 629 standard requires that each word be 16 bits and be transmitted at a fixed frequency.
In order to further define some commonality among avionics equipment suppliers, the ARINC 629 standard defines the bus and a Terminal Controller which is coupled to the bus for receiving data messages from the bus or transmitting data messages onto the bus. The ARINC 629 Terminal Controller is configured to have a known set of registers, input/output control signals, read/write control signals, and address/data lines, all of which are clearly defined so that avionic equipment suppliers may work together.